The Cheops exoplanet observation satellite made it possible to reveal for the first time the deformation of a planet – close to that of a rugby ball -, by the effect of attraction it undergoes because of its star .
The rare bird, dubbed WASP-103b, is located in the constellation of Hercules, a very modest distance of about 1,800 light years from the solar system.
The team of astronomers led by Portuguese astrophysicist Susana Barros, at the University of Porto, was looking for a specimen extremely deformed by its proximity to its star, tells AFP Jacques Laskar, co-signer of the study published on Tuesday in Astronomy & Astrophysics.
“We wanted to know if we could detect the shape of a planet by observing its transit curve”, that is to say the variation in the light of the star that it produces when passing in front of it. , explains the astrophysicist at the Paris-PSL Observatory. The idea being that if we have a planet like “a rugby ball or a soccer ball passing in front of the star, we do not have the same transit curve”.
The deformation of the planet, for its part, should then provide information on its internal structure, rather rocky or gaseous. Because “the resistance of a material to deformation depends on its composition”, noted Susanna Barros, in a press release from the European Space Agency (ESA).
To be very distorted, the planet had to be very close to its star, to better undergo the effect of attraction, called tidal force. It is this same force exerted by the Moon, and the Sun to a lesser extent, on our Earth, by periodically deforming it by a few tens of centimeters. Hence its famous form of “potato”.
The planet WASP-103b is remarkably close to its star, WASP-103. About 50 times closer to its sun than Earth is to hers. To the point of making the tour in just 22 hours, against 365 days for our blue planet.
WASP-103b thus undergoes a colossal tidal force which, failing to tear it, gives it its particularly rare form, far removed from a sphere.
The team led by Susana Barros was able to determine that if WASP-130b was one and a half times the mass of Jupiter, a gas giant in our solar system, its radius was twice as large. “So she must be very swollen due to the heating of her star and maybe other mechanisms,” said Susanna Barros.
Scientists assume that like Jupiter, it has a solid heart, enveloped in a liquid layer, surrounded by a gaseous atmosphere. But to clarify, they plan to obtain observation time with the James Webb Space Telescope.
And thus “to better understand also how she could have arrived there”, adds Jacques Laskar, convinced “that she could not have been born in this place”.